execkit-mcp 0.6.0

execkit MCP server - stateful, structured, safe shell sessions for AI agents over local shells, SSH, and Docker.

execkit-mcp

An MCP server (stdio) that exposes execkit shell sessions to any MCP-capable agent - Claude Code, Cursor, Gemini CLI, and others.

Tools

Tool	Args	Returns
session_create	transport ("local"/"ssh"/"docker"); for ssh: host, user, password or key_path, optional port, fingerprint (pin host key); for docker: container (running name/id); optional allow/deny command lists	{ "session_id": "..." }
session_exec	session_id, command, optional budget (shape output: grep/tail/head/head_tail + max_chars)	structured ExecResult JSON: stdout, stderr (split!), exit_code, duration_ms, cwd, truncated
session_destroy	session_id	{ "destroyed": true }
session_checkpoint	session_id, optional label	{ "checkpoint_id": "..." }
session_checkpoints	session_id	[{ id, label, created }]
session_restore	session_id, optional checkpoint_id	{ restored_to, files_changed }

Sessions are stateful - cd/env persist across session_exec calls. Output is ANSI-stripped, secret-redacted, and bounded; commands pass the optional policy fence before running.

Checkpoints (remote only)

On SSH/Docker sessions execkit can snapshot the workspace before changing commands and restore it on demand - a filesystem "undo." It undoes FILES only, never side effects (DB writes, network, installs).

Two requirements: git on the remote host, and an explicit workspace. Without a workspace, checkpoints and auto-snapshot are disabled - execkit will not default to the cwd or home directory (snapshotting $HOME is slow and would capture secrets). Set workspace to the project dir you want undo for (use $HOME explicitly if you really mean it).

Control it via session_create:

• workspace (root - REQUIRED to enable checkpoints)
• auto_snapshot (default true; effective only with a workspace)
• paths (sub-dirs under the root)
• checkpoint_ignores (extra gitignore-style patterns; added to the built-in defaults: .git, node_modules, build dirs, caches, .ssh, .aws, ...)

If git is absent, auto-snapshot disables itself and checkpoint calls return a clear "install git on the remote" error.

WARNING: session_restore is destructive. It reverts tracked files AND deletes ALL untracked files and directories anywhere under the workspace (via git clean), not only files created since the checkpoint. Do not restore if untracked files in the workspace must be preserved.

Output budgets

Pass budget to session_exec (or output_budget to session_create for a session default) to shape output and protect the agent's context window:

// keep the last 200 lines of a noisy build
{ "session_id": "...", "command": "npm run build",
  "budget": { "keep": { "mode": "tail", "n": 200 } } }

// grep a 50k-line log for errors, with 2 lines of context
{ "session_id": "...", "command": "cat big.log",
  "budget": { "grep": { "pattern": "error|fail", "context": 2 } } }

Shaping is line-based, client-side, and runs AFTER secret redaction; it never changes the exit code or side effects. When applied, the result includes a budget report: per-stream mode, lines_total, lines_kept.

Install

cargo install execkit-mcp        # or build from source: cargo build -p execkit-mcp

Wire it into an agent

execkit-mcp is a stdio MCP server - register the installed binary with your client. (cargo install puts it at ~/.cargo/bin/execkit-mcp; use the full path if it isn't on the client's PATH.)

Claude Code - one command:

claude mcp add execkit -- execkit-mcp        # add `-s user` to enable it everywhere

Cursor (~/.cursor/mcp.json) and Gemini CLI (~/.gemini/settings.json) - add the same block:

{
  "mcpServers": {
    "execkit": { "command": "execkit-mcp" }
  }
}

To turn on auditing or other operator settings, add an env block:

{
  "mcpServers": {
    "execkit": {
      "command": "execkit-mcp",
      "env": { "EXECKIT_MCP_AUDIT": "/var/log/execkit.jsonl" }
    }
  }
}

Then the agent can call session_create -> session_exec -> session_destroy.

Example session (what the agent sees)

// session_create {"transport":"local"}              -> {"session_id":"sess_1"}
// session_exec   {"session_id":"sess_1","command":"npm run build"}
//   -> {"stdout":"...","stderr":"Error: Cannot find module 'webpack'",
//       "exit_code":1,"duration_ms":3420,"cwd":"/home/u/app","truncated":false}

Security model

The agent driving these tools can be prompt-injected, so tool arguments are untrusted. Anything dangerous to the host/filesystem is therefore controlled by the operator at startup (env vars), not by per-call agent arguments:

Env var	Purpose	Default
EXECKIT_MCP_AUDIT	append a JSONL audit log of every command here	off
EXECKIT_MCP_KEY_DIR	SSH key_path must canonicalize to inside this dir	~/.ssh
EXECKIT_MCP_KNOWN_HOSTS	SSH host-key verification file (TOFU; rejects changed keys)	~/.ssh/known_hosts
EXECKIT_MCP_INSECURE_ACCEPT_ANY_HOSTKEY	DANGEROUS - disable host-key checks	unset
EXECKIT_MCP_MAX_SESSIONS	soft cap on concurrent live sessions	64
EXECKIT_MCP_SESSION_TTL	reap sessions idle longer than this many seconds (frees the process + cap slot); 0 disables	1800 (30 min)

• Host keys are verified by default (TOFU against known_hosts; a changed key is rejected as a likely MITM). Pass a fingerprint to require an exact key, or set the insecure env var only for throwaway/test hosts.
• key_path is sandboxed to EXECKIT_MCP_KEY_DIR; out-of-bounds/traversal paths are rejected with a generic error (no path-existence leak).
• Audit destination is operator-chosen, never a tool argument (prevents an injected agent from writing to arbitrary files).
• Docker sessions run docker exec against any container the daemon can see, so the agent reaches whatever your docker context exposes. Grant the server Docker access only when you want that, and scope the daemon/context accordingly.
• The server speaks MCP on stdout; all diagnostics go to stderr.
• Use allow/deny for a command fence, and run the agent + SSH user with least privilege. The fence is advisory - defense in depth, not a sandbox.

Apache-2.0.